LXR linux/arch/mips/rb532/time.c

   1/*
   2 * Carsten Langgaard, carstenl@mips.com
   3 * Copyright (C) 1999,2000 MIPS Technologies, Inc.  All rights reserved.
   4 *
   5 *  This program is free software; you can distribute it and/or modify it
   6 *  under the terms of the GNU General Public License (Version 2) as
   7 *  published by the Free Software Foundation.
   8 *
   9 *  This program is distributed in the hope it will be useful, but WITHOUT
  10 *  ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
  11 *  FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  12 *  for more details.
  13 *
  14 *  You should have received a copy of the GNU General Public License along
  15 *  with this program; if not, write to the Free Software Foundation, Inc.,
  16 *  59 Temple Place - Suite 330, Boston MA 02111-1307, USA.
  17 *
  18 *  Setting up the clock on the MIPS boards.
  19 */
  20
  21#include <linux/init.h>
  22#include <linux/kernel_stat.h>
  23#include <linux/ptrace.h>
  24#include <linux/sched.h>
  25#include <linux/spinlock.h>
  26#include <linux/mc146818rtc.h>
  27#include <linux/irq.h>
  28#include <linux/timex.h>
  29
  30#include <asm/mipsregs.h>
  31#include <asm/time.h>
  32#include <asm/mach-rc32434/rc32434.h>
  33
  34extern unsigned int idt_cpu_freq;
  35
  36/*
  37 * Figure out the r4k offset, the amount to increment the compare
  38 * register for each time tick. There is no RTC available.
  39 *
  40 * The RC32434 counts at half the CPU *core* speed.
  41 */
  42static unsigned long __init cal_r4koff(void)
  43{
  44        mips_hpt_frequency = idt_cpu_freq * IDT_CLOCK_MULT / 2;
  45
  46        return mips_hpt_frequency / HZ;
  47}
  48
  49void __init plat_time_init(void)
  50{
  51        unsigned int est_freq;
  52        unsigned long flags, r4k_offset;
  53
  54        local_irq_save(flags);
  55
  56        printk(KERN_INFO "calculating r4koff... ");
  57        r4k_offset = cal_r4koff();
  58        printk("%08lx(%d)\n", r4k_offset, (int) r4k_offset);
  59
  60        est_freq = 2 * r4k_offset * HZ;
  61        est_freq += 5000;       /* round */
  62        est_freq -= est_freq % 10000;
  63        printk(KERN_INFO "CPU frequency %d.%02d MHz\n", est_freq / 1000000,
  64               (est_freq % 1000000) * 100 / 1000000);
  65        local_irq_restore(flags);
  66}
  67